In this issue: What’s Inside a Black Hole’s Horizon?, Cosmic-Ray Positrons Limit Dark Matter Models, Heisenberg Vindicated
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What’s inside a black hole’s horizon?
New theoretical work rekindles the controversy over whether black holes have a “firewall” that would destroy any observer crossing the event horizon.
In 2012, a group of physicists at the University of Santa Barbara proposed that an observer falling inside a black hole would be destroyed by a firewall - a sea of high-energy quanta at the event horizon. Their idea was intended to solve certain inconsistencies in black-hole theory, but it sparked a heated debate among theoretical physicists: firewalls violate Einstein’s well-established equivalence principle, which says that an observer can’t distinguish between inertial motion and free fall and therefore shouldn’t be able to tell if he has passed the event horizon. Two of the original firewall proponents have now provided further arguments - based on a theoretical reconstruction of the interior of a black hole - to support the firewall hypothesis.
* Donald Marolf, Joseph Polchinski (contact author), “Gauge-gravity duality and the black hole interior”, Physical Review Letters (expected publication date: Oct 21)
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Cosmic-Ray Positrons Limit Dark Matter Models
An analysis of recent data from the Alpha Magnetic Spectrometer (AMS) provides new constraints on the nature of dark matter particles.
In spring 2013, the space-borne AMS - a detector on the International Space Station designed to look for unusual matter (antimatter and dark matter) - delivered its first data, confirming an unexplained excess of cosmic-ray high-energy positrons (the antiparticles of electrons). According to certain models, these positrons could be a signature of the decay or annihilation of dark-matter. A team of researchers from Sweden, Germany, the US and the Netherlands has now analyzed the AMS data to derive a set of constraints on the nature of possible dark matter particles, providing a 100-fold improvement of the current limits on certain dark matter parameters. The results significantly limit the range of models that may contain a viable candidate for dark matter
* L Bergström, Torsten Bringmann (contact author) et al, “New limits on dark matter annihilation from AMS cosmic ray positron data”, Physical Review Letters (expected publication date: Oct 21)
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Heisenberg Vindicated
Heisenberg originally formulated his uncertainty principle in terms of the “observer effect”: a relationship between the precision of a measurement and the disturbance it creates. But in a number of recent experiments, researchers have claimed experimental errors below the Heisenberg limit, arguing the precision-disturbance relationship can be violated. Now, a team of researchers from the UK, Finland and Germany has reported a new formulation of the uncertainty principle, which should have general validity provided that the measurement error is properly defined.
* Paul Busch (contact author), P Lahti, RF Werner, “Proof of Heisenberg’s error-disturbance relation”, Physical Review Letters (expected publication date: Oct 17)
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Journal articles and preprints are available to journalists on request.
Matteo Rini, PhD
Deputy Editor, Physics
